A. Golf Ball Construction and Composition
Modern golf balls generally comprise a core and at least one additional outer layer. Two-piece balls, having a cover around a solid, often single-piece, spherical rubber core, provide high initial speeds but relatively low spin rates, and hence perform well for drives and other shots made using woods, but do not perform as well for shots made with short irons where distance is less important and high spin rate is desirable. Ball performance can be modified, particularly the travel distance and the feel transmitted to the golfer through the club, by including additional layers between the core and outer cover layer. A three-piece ball has one additional layer between the core and outer cover layer, a four-piece ball has two additional layers between the core and outer cover layer, and so on.
The compositions that are used to make particular golf ball layers also can significantly affect golf ball performance. Compositions can be modified to vary, for example, polymer hardness, compression, resilience and/or durability. Most modern golf balls now utilize core compositions made from synthetic rubbers based on polybutadiene, especially cis-1,4-polybutadiene. To vary core properties the polybutadiene often is further formulated with crosslinking agents, such as sulfur or peroxides, or with co-crosslinking agents, such as zinc diacrylate. The weight and hardness of the core may be further adjusted by incorporating various filler materials.
Polyalkenamers, which typically include a linear polymeric component and a significant fraction of cyclic oligomer molecules to lower their viscosity, also are useful for making golf balls. Compounds of this class can be produced in accordance with the teachings of U.S. Pat. Nos. 3,804,803, 3,974,092 and 4,950,826, the entire contents of all of which are incorporated herein by reference. Additional compositions for forming golf balls are disclosed in applicants' copending provisional applications, Nos. 60/646,669 and 60/706,562, both of which applications are incorporated herein by reference.
B. Golf Ball Compositions Comprising Peptizers
A variety of materials other than polymers or rubber, such as fillers and processing aids, are commonly used to make golf balls. Small amounts of chemical peptizers, for example, have been incorporated into golf ball cores to accelerate polybutadiene rubber softening under the influence of a mechanical force, heat, or a combination thereof. As used herein, a peptizer is a compound or composition that inhibits cross-linking during the initial processing of unsaturated polymers, but which then participates in the cross-linking of the unsaturated polymer after cross-linking has commenced. A wider array of active chemical ingredients and fillers can be incorporated into a composition when peptizers are used relative to compositions formulated without peptizers. Peptizers also facilitate processing compositions, such as by lowering processing temperatures.
Particular peptizers are known for making polymer compositions, including golf ball compositions. For example, U.S. Pat. No. 4,955,966, states that the “rubber composition of the present invention may be incorporated with various known additives, for example, vulcanization accelerator, vulcanization retarder, antioxidant, plasticizer, peptizer, tackifier, antitack agent, sponging agent, dispersant, dusting agent, mold release agent, solvent, softening agent and the like.” The '966 patent, column 10, lines 3-9, (emphasis added). This is the only disclosure provided by the '966 patent concerning peptizers. The majority of patents that disclose using peptizers to make golf ball compositions do not provide information or otherwise identify particular peptizers useful for making such compositions.
A few patent documents do disclose specific peptizer compounds. For example, U.S. Pat. No. 5,948,862 discloses using diphenyl disulfide peptizers. U.S. Pat. Nos. 6,569,037, 6,692,379 and 6,905,423 disclose using zinc salts of pentachlorothiophenol. The '423 patent specifically states that:                The soft intermediate layer may also contain additives, fillers, thickeners, or a combination thereof, to adjust the specific gravity of the layer to alter various golf ball properties as needed or desired. “RENACIT” 7 is a peptizer produced by Miles, Inc. of Pittsburgh, Pa., that is a pentachlorothiophenol mixture containing Kaolin, quartz, and mineral oil. Materials such as “RENACIT” 7 can be used to alter the properties of the inner surface of the mantle layer. Specifically, it can be used to soften the inner surface.The '423 patent, column 12, lines 32-39.        
TaylorMade® also has several issued patents and patent applications that discuss using peptizers for making golf ball compositions, including U.S. application Ser. No. 10/926,509, entitled “Golf Balls Incorporating Nanofillers,” and U.S. application Ser. Nos. 10/662,619, 10/662,626, 10/662,628 and 10/662,719, entitled “Golf Balls Incorporating Peptizers and Method of Manufacture.” Each of these prior TaylorMade® applications is incorporated herein by reference. These prior applications state, for example, that:                Peptizers can be defined as chemicals that inhibit cross-linking during the processing of unsaturated polymers. The peptizer can further participate in the cross-linking of the unsaturated polymer when cross-linking does begin. The peptizer comprises an organic sulfur compound and/or its metal or non-metal salt. Examples of the organic sulfur compound include: thiophenols, such as pentachlorothiophenol and its metal and non-metal salts, 4-butyl-o-thiocresol, 4 t-butyl-p-thiocresol, and 2-benzamidothiophenol; thiocarboxylic acids, such as thiobenzoic acid; 4,4′ dithio dimorpholine; and, sulfides, such as dixylyl disulfide, dibenzoyl disulfide; dibenzothiazyl disulfide; di(pentachlorophenyl)disulfide; dibenzamido diphenyldisulfide (DBDD), and alkylated phenol sulfides, such as VULTAC marketed by Atofina Chemicals, Inc. of Philadelphia, Pa. Examples of the metal salts of an organic sulfur compound include zinc salts of the above-mentioned thiophenols and thiocarboxylic acids. Examples of non-metal salts of an organic sulfur compound include the amine or ammonium salts of the above-mentioned thiophenols and thiocarboxylic acids. Preferred peptizers include pentachlorothiophenol, its metal salts, and its non-metal salts, and dibenzamido diphenyldisulfide. Peptizers can be used alone or in an admixture of two or more peptizers.        